The present invention relates to a friction device for a railway car truck and more particularly to a novel device which serves to force a winged friction shoe to rock about a vertical axis to align the friction surface on the shoe with the friction surface of a friction plate should these surfaces be initially in a laterally non-parallel relationship.
The present apparatus is an improvement of the apparatus described in U.S. Pat. No. 2,953,995 issued Sept. 27, 1960 which is incorporated herein by reference thereto.
The type of railway car truck to which the present invention relates comprises, generally, spaced side frame members each having an opening arranged to resiliently support opposite ends of a bolster. A spring biased friction shoe has a wall engageable with a friction surface on the side frame. The friction shoe also includes flanges or wings which project laterally from a body portion and bear against guiding surfaces on the bolster. The shoe frictionally engages both the side frame and bolster for controlling the oscillating movement of the latter. Heretofore, the wings and guiding surfaces were constructed and arranged so that the friction wall of the shoe was constrained for movement in a plane parallel to the longitudinal axis of the bolster.
In some instances and under certain operating conditions the side frame column friction plate is not aligned in a parallel relationship to the longitudinal axis of the bolster. When this occurs the friction wall of the shoe will not bear squarely against the side frame column friction plate thereby greatly decreasing the bearing area. This causes the friction shoe and side frame column friction plate to wear unevenly thereby shortening the service life of both.
It is a primary object of the present invention to provide a railway car truck with a friction shoe constructed and arranged to overcome the difficulties encountered heretofore and thereby improve the service life and reliability thereof.
According to the present invention this is accomplished by providing friction shoe wings with surfaces that are inclined with respect to the guiding surfaces that they engage so that the wings initially contact the guiding surfaces at a point adjacent the friction shoe spring pocket. When the friction surface on the side frame is not laterally parallel to the friction wall of the shoe, a rotational couple force is created that causes the friction shoe to rock about a vertical axis until the friction wall of the shoe bears squarely against the friction surface on the side frame.